1. Field of the Invention
This invention relates to a projectile of an ammunition round and, in particular, to the attachment of a driving band to the projectile.
2. Prior Art
Driving bands on projectiles are slightly radially enlarged portions of the projectile which act to obturate the barrel thus providing a seal so that the expanding gases from the firing of the ammunition round can drive the projectile through the barrel. Further, the driving band is engraved through interference with the rifling and causes the projectile to spin. This acts to stabilize the projectile so that it may be propelled accurately.
It is known to use copper or soft iron bands for such driving bands but these tend to wear the barrel quickly. The use of plastic for driving bands is also known. However, there has been difficulty in attaching these plastic driving bands to the projectile. One known relatively expensive method is to spray a porous metal onto the projectile and then mold the plastic in place. The plastic would tend to interlock with the porous metal so as to secure the plastic to the projectile. This interlock is hard to obtain. The interlock cannot be relied upon due to variability of processing parameters. Such processing parameters include having sufficient porosity in the sprayed-on metal so the plastic can be received. Also, the use of sprayed-on metal requires an additional interface that can separate from the projectile. The uniformity and reliability of the interlock cannot be readily verified without destructive testing.
Some bands have been secured to the projectile body through the use of various dovetail configurations in the projectile body. Such configurations require a band depth of approximately 0.050 inch. This is a significant disadvantage in the design of a projectile body because the wall thickness at the band area of the projectile body must be increased. This adds to the weight of the projectile and reduces the amount of explosive that can be stored inside the projectile body. Attempts were made to solve this problem by using either a metal sprayed surface or a wire mesh attached to the projectile to provide a porous surface for retention of the driving bands. Neither of these approaches were fully successful due to failure of either the primary or secondary attachments, or an inability to verify consistency of the attachments.
There still remains a need for a simple, secure mechanical coupling of the driving band to the projectile. In accordance with this invention, driving bands are able to perform at higher velocities and withstand the more harsh environment of telescoped ammunition. Other systems used in the past (copper bands, soft iron bands, plastic bands with deep dovetails, etc.) will not perform adequately in this environment at shallow seat depths.